Decontamination apparatus

ABSTRACT

A closed system for automatically decontaminating various articles, including hollow bags and tubing, by washing and disinfecting them with a liquid chemical disinfectant, using the same tub for both washing and disinfection. The articles are automatically agitated in the washing and disinfecting liquids to loosen dirt and assure complete wetting of their inside and outside surface by the disinfectant. Containers are provided for mounting the hollow articles for agitation and spinning from the same shaft, preferably in baskets provided for this purpose, and for holding them in positions which will assure their thorough washing, disinfecting and emptying. A unique storage and transfer system is employed for the disinfectant supply and this includes a novel diverter or transfer valve for connecting to the tub drainage system. The apparatus preferably uses a disinfectant supply which has a relatively long life and is used over and over again in successive decontaminating cycles and has a use cycle timing device for rendering the apparatus inoperative at the end of a given use cycle for the disinfectant. A device is provided for again rendering the apparatus operative after a new supply of disinfectant is substituted for the old. Various other timing and control features are provided.

United States Patent [1 1 Fry et a1.

[4 1 May 20, 1975 1 DECONTAMINATION APPARATUS [73] Assignee: Arbrook, lnc., Arlington, Tex.

[22] Filed: Oct. 20, 1972 [21] Appl. No.: 299,528

Related U.S. Application Data [62] Division of Ser. No. 49,407, June 24, 1970, Pat. No.

[52] US. Cl. 137/565; 137/572; 417/17; 68/D1G. 2; 134/157 [51] Int. Cl ..B08b 3/06; B08b/9/00; BOSb/ll/OZ [58] FieldofSearch...137/572,565;4l7/40,44,217; 68/12 R, 12 FA, 9; 134/9 A, 96,101,

GS/DIG. 2, 207, 208; 137/387 Primary ExaminerWilliam R. Cline [5 7] ABSTRACT A closed system for automatically decontaminating various articles, including hollow bags and tubing, by washing and disinfecting them with a liquid chemical disinfectant, using the same tub for both washing and 1 disinfection. The articles are automatically agitated in the washing and disinfecting liquids to loosen dirt and assure complete wetting of their inside and outside surface by the disinfectant. Containers are provided for mounting the hollow articles for agitation and spinning from the same shaft, preferably in baskets provided for this purpose, and for holding them in positions which will assure their thorough washing, disinfecting and emptying. A unique storage and transfer system is employed for the disinfectant supply and this includes a novel diverter or transfer valve for connecting to the tub drainage system. The apparatus preferably uses a disinfectant supply which has a relatively long life and is used over and over again in successive decontaminating cycles and has a use cycle timing device for rendering the apparatus inoperative at the end of a given use cycle for the disinfectant. A device is provided for again rendering the apparatus operative after a new supply of disinfectant is substituted for the old. Various other timing and control features are provided.

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The present invention relates to the decontamination or the washing and disinfecting of contaminated equipment, and more particularly to the decontamination of generally hollow equipment which may be in the form of tubing, bags, or the like, especially when the equipment is formed of rubber, plastic, metal or some other substantially moisture impermeable material such as is used primarily in hospitals and medical offices for anesthesia, inhalation therapy, etc.

Equipment of this type is subject to direct contamination through contact with each patient and often contains deposits of blood, mucous, vomit, etc. Thus, when this contamination is evident, it has been the custom to attempt to wash by hand. the large variety of plain and corrugated tubing, airways, breathing bags, mouth pieces and other hollow articles which are used. Unfortunately, however, these visible deposits are only one type of contamination and merely serve to point to the real problem which is the infection of this equipment with bacteria, bacilli, viruses, spore formers and other pathogenic microorganisms harbored by different patients. Furthermore, a particular item of equipment may appear quite clean, even directly after washing and actually be highly infected with pathogens. It seems clear, therefore that there is a great need for hospital apparatus which will fully decontaminate, or both wash and disinfect this type of equipment.

One of the problems in providing this type of apparatus, however, is that most of the hospital anesthesia and inhalation therapy items to be disinfected, for example, are made, at least in part, of flexible, heat-sensitive materials such as natural or synthetic rubber, plastic, or the like. Thus, they cannot be sterilized or effectively disinfected in the normal heat sterilizing equipment available at hospitals, assuming this type of equipment could be adapted for this purpose. Although gas sterilization could be used to disinfect once the articles are clean, suitable apparatus for both washing and gas sterilizing this type of hollow tubing and other equipment has not been developed.

One attempt at solving this problem is disclosed in British Pat. No. l,l68,035, wherein apparatus is suggested specifically for washing and decontaminating the hollow tubing, breathing bags, etc. forming part of typical hospital anesthesia equipment. This device forces pressurized hot water through the various hollow articles and mentions that the articles finally are disinfected by raising the temperature of the water to 190 F., which, it is said, is sufficient to kill bacteria without injuring the rubber or rubber-like material from which the articles are formed. While there may be some articles which are not adversely affected by a temperature of 190 F., there are many others such as the plastic tubing used in inhalation therapy which definitely would soften at these temperatures. The tubing to be washed must be individually positioned over spaced pipes through which the hot water is projected into the tubing. Then, for those items which do not fit on the piping provided, hot water is sprayed around the interior of the unit by an impeller such as used in a modern dishwasher. There is no mention in this patent of how the decontaminated articles are freed of water and dried or the special problems presented in emptying the different types of tubing used in anesthesia.

We have invented a single decontaminating unit which automatically washes and disinfects hollow articles of the type described using a cold liquid disinfectant. First, the articles are washed free of solid contaminants, such as dried blood and mucous, and rinsed, then they are disinfected by immersing them in a chemical disinfecting solution without the application of heat. Following the disinfecting step, the decontaminated items are thoroughly rinsed of the disinfecting liquid and then emptied of the rinsing liquid automatically, again without the need to use heat.

Our decontaminating unit comprises a working tub adapted to hold supplies of washing liquid and liquid disinfectant, respectively, in successive washing and disinfecting steps in the decontaminating cycle for a given set of articles, and a storage tank which holds the disinfectant supply during the washing step. The disinfectant preferably is transferred back and forth be tween the tank and the tub by a disinfectant piping system which is adapted to be completely sealed off from the tub when not in use for this purpose and includes its own 'pump.

Our apparatus preferably uses a chemical disinfecting solution which has a relatively long effective life so that a given supply of disinfectant will remain effective for quite some time and during many decontaminating cycles in the apparatus of this invention. For instance, a practical use or life cycle for a given supply of a preferred type of sterilizing solution based upon activated glutaraldehyde is 14 days, as compared with a single decontaminating cycle lasting about minutes. Preferably, both the individual decontaminating cycle and the disinfectant use cycle are automatically timed, the latter by use cycle timing means which renders the apparatus inoperative at the end of a given cycle time following the introduction ofa first supply of disinfectanat in said apparatus. Then the apparatus includes means for activating the timing means to again render the apparatus operative after the first supply is removed and a new supply of disinfectant is introduced therein. Provision is made for completion of any decontaminating or disinfecting cycle which happens to be in progress at the end of the use cycle time so that the apparatus does not become inoperative until the decontaminating cycle has ended.

When a chemical disinfecting liquid having a relatively long normal effective life (such as 14 or more days) is intended to be used over and over again in successive decontaminating cycles, it is highly important to avoid or minimize dilution or contamination of the disinfectant in each of these cycles since any appreciable dilution or contamination will be cumulative and render the disinfectant ineffective long before the end of its normal effective life. It therefore is important that the tub and the hollow articles to be decontaminated be completely emptied of any washing or rinsing liquid prior to placing the disinfectant in the tub and that the disinfectant be effectively removed from each of the articles and from the tub at the end of the disinfecting cycle, all as describedhereinafter. Similarly, it is important that the disinfectant supply be sealed off from the water or other liquid going through the unit during the washing and rinsing cycles and that no washing, rinsing or disinfecting liquid be trapped in the common parts of the system. The method and apparatus of this invention insure that dilution and contamination of the disinfectant will be minimized to prevent shortening its normal use or life cycle time, as explained hereinafter.

In the preferred embodiment of this invention, hollow articles to be decontaminated are positioned and held in relatively fixed positions in retaining means drivably mounted from a drive shaft entering the working tub, the tub is filled with a washing fluid such as water and detergent, and then the shaft is rotated back and forth by oscillating means first in one direction and then in the other to reciprocate the articles through the washing liquid so that the liquid and the articles are agitated with respect to one another. When the washing step is completed, the tub is emptied and the drive shaft is spun relatively rapidly in one direction to remove residual washing liquid substantially completely from the hollow articles by centrifugal force. It is an important feature of this embodiment of our invention that the hollow tubing or other articles are so positioned in the retaining means that the washing liquid is forced into the articles during the above-described oscillation or agitation and yet removed therefrom by centrifugal force when the shaft is spun. This occurs when the axes of the end portions of the hollow articles extend in a generally trailing spiral configuration or radially outwardly and obliquely away from the radii of the drive shaft in an angular direction opposite to the direction in which the shaft is spun.

Following removal of the washing liquid, the articles are thoroughly rinsed in a rinsing step which normally includes immersion in the rinsing fluid and agitation therein as described above in connection with the washing step. As in the washing step, the articles are spun after the rinsing fluid has been removed from the tank, to remove residual liquid substantially completely from the articles. Single or multiple rinsing steps may be used to minimize contamination of the disinfectant with the washing liquid. When the articles are sumciently rinsed, the disinfectant supply is transferred from the storage tank to the tub so that the articles are completely immersed in the disinfectant liquid. Then the articles are agitated in the disinfectant for a given period of time, say about l to minutes, to free any entrapped air and assure that the liquid disinfectant thoroughly wets all internal and external surfaces. At the end of the disinfecting step, the disinfectant supply is transferred back to the storage tank with residual disinfecting liquid being removed from the articles by spinning as described hereinbefore in connection with the washing and rinsing steps. Then, the articles are thoroughly rinsed to remove any residual traces of the disinfectant and finally spun dry by the same centrifugal technique described hereinbefore.

According to the preferred embodiment of this invention, the working tub drains into a diverter valve which connects the tub either to a drainage system or to the disinfectant piping system. The drainage system includes a drainage pump which removes washing and rinsing liquids from the tub when the diverter valve connects the tub to the drainage system, and the disinfectant system includes a reversible disinfectant pump which transfers the disinfectant from the tank to the tub when the diverter valve connects the tub to the disinfectant system and then returns the disinfectant to the tank at the end of the disinfectant step as described above. Preferably, also, the disinfectant pump will not run unless it is immersed in the disinfectant liquid and the operation of the pump is controlled for this purpose by a pair of fluid level responsive switches, one between the tank and the pump and the other between the diverter valve and the pump. The diverter valve positively seals off the drainage system when the tub is connected to the disinfectant system to prevent any possible loss of disinfectant and positively seals off the disinfectant system to prevent contamination of the disinfectant when the tub is connected to the drainage system. It also is important that the diverter valve is designed so that it drains free and does not trap liquid and thereby contaminate or dilute the disinfectant due to passage of the several liquids through the same valve.

In a preferred embodiment of our invention, the use cycle timing means for the disinfectant supply is rendered operative following the end of a given use.cycle only when the new supply of liquid introduced reaches a predetermined amount or liquid level in the apparatus.

Preferably, also the apparatus includes means for resetting the use cycle timing means at this point so that it is ready to again time another decontaminating or disinfecting use cycle. This resetting means may be a reset timer operating in a timing circuit with the use cycle timer which may, in turn, comprise a period timer and a stepping timer with the stepping timer counting the periods covered by the period timer. In this way, accurate control of the various cycles may be maintained over a relatively long period of time such as the 14 days corresponding to the normal use cycle of a preferred type of disinfectant liquid.

in order to insure that the disinfectant use cycle is properly timed and also that the disinfectant is not wasted, safety means is provided for preventing removal of the current disinfectant supply from the apparatus prior to the end of its use cycle or at least a given time increment prior thereto. It also is desirable to provide emergency pump out or emptying means to remove the disinfectant from the unit at any time. However, the emergency means should not be too readily activatable and preferably should in some way initiate resetting of the timing means so that the timing means is again ready to operate after the old disinfectant has been replaced with a new supply.

Another advantage of the apparatus of this invention is that the retainers or baskets for holding the articles to be washed may be specifically designed to hold a particular type of equipment such as the various tubings, airways and bags used in anesthesia or the elongated tubing, bottles and the like used in inhalation therapy under ordinary hospital procedures. In fact, the baskets may be designed to mount and hold the various articles so that each article is disposed in such a way that when it is agitated in the tub, the particular washing, rinsing or disinfecting liquid will be forced in and out of the hollows of the article to displace any air pockets and assure that all internal and external surfaces of the article are thoroughly wetted therewith as described hereinbefore, and yet assure that the articles and particularly the end portions thereof are arranged in the proper configuration with respect to the drive shaft so that residual fluid will be removed from the article by centrifugal force when the shaft is spun in one direction at relatively high speed.

Other and further advantages of this invention will appear to one skilled in the art from the following description and claims taken together with the drawings wherein:

FIG. I is a view in perspective of a decontaminating unit according to a preferred embodiment of this invention.

FIG. 2 is an enlarged front view. partly in section and partly in elevation, taken along the line 22 of FIG. 1, showing the interior of the unit and most of its important working parts, including the retaining basket for holding the articles to be decontaminated in the working tub.

FIG. 3 is a more greatly enlarged top plan view, taken along the line 3-3 of FIG. 2, through the opening in the gear box of the driving mechanism of this unit.

FIG. 4 is a front view, partly in section and partly in elevation, taken along the line 44 of FIG. 3, and showing the drive pulley in its lowermost position in which it oscillates the drive shaft supporting the retaining basket for the articles to be decontaminated.

FIG. 5 is a similar view, partly in section and partly in elevation, showing only the lowermost part of the apparatus with the drive pulley in its uppermost position in which it spins the drive shaft and the basket counterclockwise.

FIG. 6 is a schematic piping diagram of the liquid transfer system of the embodiment of the foregoing figures.

FIG. 7 is a more greatly enlarged top view, partly in section and partly in plan, taken along the line 77 of FIG. 2 and showing the interior of the diverter valve for controlling the flow of liquid from the working tub.

FIG. 8 is a similar view, partly in section and partly in elevation, taken along the line 8-8 of FIG. 7.

FIG. 9 is an exploded view ofa preferred form of retaining basket for decontaminating anesthesia equipment in accordance with this invention.

FIG. 10 is a enlarged top plan view of the basket of FIG. 9 with the cover removed.

FIG. 11 is a view partly in section and partly in elevation taken along the line 11-11 of FIG. 10.

FIG. 12 is a somewhat reduced top plan view of the basket of FIG. 10 showing one set of anesthesia equipment arranged therein in the positions for which the basket is designed.

FIG. 13 is a top plan view of the basket of FIG. 12 with its three cover segments in position thereon but without showing the equipment it contains.

FIG. 14 is a somewhat enlarged view partly in section and partly in elevation taken along the line 14-14 of FIG. 12.

FIG. 15 is a greatly enlarged view partly in section and partly in elevation taken along the line 15-15 of FIG. 10.

FIG. 16 is a similar view partly in section and partly in elevation taken along the line l6l6 of FIG. 10 and showing a portion of the basket structure.

FIG. 17 is a similar view, partly in section and partly in elevation, taken along the line l7l7 of FIG. 13.

FIG. 18 is a view, partly in section and partly in elevation, taken along the line 1818 through the cover in FIG. 13.

FIG. 19 is a view, partly in section and partly in elevation, taken along the line 19-l9 of FIG. 10.

FIG. 20 is a top plan view of a retaining basket for holding inhalation therapy equipment according to another preferred embodiment of this invention, with its cover off.

FIG. 21 is a view, partly in section and partly in elevation. taken along the line 21-21 of FIG. 20.

FIG. 22 is an exploded view of the main parts of the retaining basket of FIG. 20.

FIG. 23 is a somewhat reduced top plan view of the basket of FIGS. 20-22 with its cover removed and with one complete set of inhalation therapy equipment held in position therein.

FIG. 24 is a top plan view of the basket of FIG. 23 with its cover on but without showing the equipment it contains.

FIG. 25 is a view, partly in section and partly in elevation, taken along the line 2222 of FIG. 24.

FIG. 26 is a more greatly enlarged view, partly in section and partly in elevation, taken along the line 2626 of a portion of the inhalation therapy basket of this invention showing inhalation therapy equipment in position therein.

FIG. 27 is a similarly enlarged view, partly in section and partly in elevation, taken along the line 27-27 of FIG. 26 and showing one means for retaining the inhalation therapy bottles in their proper positions.

FIG. 28 is a similar view, partly in section and partly in elevation, taken along the line 2828 and showing another means for holding the inhalation therapy bottles in position.

FIG. 29A shows the cam diagram for the main control timer for the decontamination unit of the foregoing figures along with portions of the wiring diagram connected to the cams involved.

FIG. 29B is another portion of the wiring diagram associated with the main control timer which fits to the right of FIG. 29A as illustrated by the arrows in both of these figures.

FIG. 29C is the wiring diagram for the disinfectant use cycle timing system which also is associated with the main control timer and fits to the right of FIG. 298 as indicated by the arrows in both of these figures.

FIG. 30 shows the cam diagram for the reset (5 minute) timer for the disinfectant use cycle timing system.

FIG. 31 shows the cam diagram for the period (l2 hour) timer for the disinfectant use cycle timing system.

FIG. 32 shows the cam diagram for the stepping (14 day) timer of the disinfectant use cycle timing system.

INTRODUCTION Referring to the drawings, and FIG. 2, in particular, there is shown a preferred decontaminating unit of this invention which comprises a working tub 41 in which the articles to be decontaminated are first washed and then disinfected by immersion in a liquid chemical disinfectant, a retaining basket 42 in which the articles are mounted and held during washing and disinfection, a drive shaft 43 on which the basket is mounted for oscillation and for spinning, and a storage tank 44 for holding the liquid disinfectant when it is not needed in the tub 41.

The working tub 41 and the disinfectant tank 44 each are disposed inside a cabinet 45 having a front wall 46, a back wall not shown and opposed side walls 47. A pair of hinged covers, i.e., a tub cover 48 and a tank cover 49, are provided to enclose the unit while at the same time offering easy access to the tub 41 and the tank 44, respectively. A control console 51 for operating the unit is mounted on legs 52 supported by a cross member 53 from which the covers 48 and 49 are hinged along the back wall of the unit. The tub 41 is supported on a tripod consisting of three metal legs 54 bolted to the bottom of the tub. The legs 54 are inclined inwardly towards their lower extremities where they join a foundation ring 55 which, in turn, is secured to a horizontal foundation plate 56 which is elevated somewhat above the bottom edges of the cabinet. The foundation plate 56 is supported by six legs 57, one at each of its corners, each of which in turn is secured to an angle bar 58 extending inwardly from one of the side walls of the cabinet. The disinfectant tank 44 is mounted on a pair of horizontal angle irons 59, only one of which is shown in FIG. 2, and each angle iron is supported at each of its ends by a vertical leg 61. The resulting four vertical legs 61 extend downwardly to the horizontal foundation plate 56 and are secured thereto.

The apparatus of this embodiment is adapted to operate automatically, as will be explained more fully hereinafter in conjunction with the diagrams of FIGS. 29A, 29B, 29C, 30, 31 and 32, to successfully wash, rinse, disinfect, rinse again and then empty (of liquid) a set of initially contaminated equipment placed therein for treatment during an automatically timed decontamination cycle.

During the decontamination cycle, the drive shaft 43 and the basket 42 containing the equipment are rotatively oscillated in the tub 41 during washing, deep rinsing and disinfecting, and are spun relatively rapidly in one direction at several points during the cycle to empty the equipment of liquid. As will be explained more fully hereinafter in conjunction with the description of FIGS. 9-28, the retaining basket 42 is especially designed to receive particular types or sets of hollow articles of equipment, such as anesthesia and inhalation therapy equipment, and hold them in specific positions which will cause the liquid to circulate through them during the aforesaid agitation and to empty from them when the basket is spun.

Basket Drive The retaining basket 42 is drivably mounted for rotation with and on the drive shaft 43 by a keyway 62 which rotatably connects the shaft with the spindle 63 of the basket and rests on a horizontal annular ring 64 welded to the drive shaft. The drive shaft 43, in turn, is mounted for rotation in a vertical stuffing box bearing 65 at the bottom of the tub. The bearing 65 includes a single ball bearing race 66 and a packing gland 67 for assuring that no leaks occur where the shaft 43 passes through the tub 41. The lower end of the drive shaft 43 extends into a gear box 68 welded to, and therefore adapted to rotate with, a vertical outer shaft 69 which extends downwardly from the bottom of the gear box and thence through a hole 71 in the foundation plate 56. The lower end of the outer shaft 69 is rotatably mounted in a cylindrical brake 72 which is fixed to the underside of the foundation plate 56. The upper end of the outer shaft 69 is rotatably mounted from the drive shaft 43 through the gear box 68 which has a bolted cover plate 73 rotatably mounted on the lower end of the drive shaft through another ball bearing race 74 fitted between the drive shaft 43 and the cover plate 73. Rotation of the gear box 68 is counterbalanced by a counterweight 75 bolted to a horizontal extension 76 of the gear box cover plate. The drive shaft 43 is positioned vertically by a pair of spaced thrust rings 77 fixed to the drive shaft under each of the bearing races.

The cylindrical brake 72 operates in a conventional manner to normally brake or prevent the outer shaft 69, and therefore the gear box 68, from rotating, as shown in FIG. 4. The brake is adapted to be released to allow the outer shaft 69 to rotate when a brake release cylinder 78 at the bottom of the brake is thrust upwardly as shown in FIG. 5.

An inner intermediate shaft 79 extends upwardly through the brake 72 and the outer shaft 69 into the gear box 68 and is mounted for rotation therein. A drive pulley 81 is mounted at the lower end of the intermediate shaft through mating square helical male threads 82 on the intermediate shaft and female threads in the drive pulley. Thus, when the pulley 81 is rotated it will tend to move helically along the threads and if it is restrainend from moving axially it will rotate the intermediate shaft 79.

Referring to FIG. 2, it will be seen that a drive motor 83 mounted on the foundation plate 56 drives a power pulley 84 mounted at the end of a short power shaft 85 extending from the drive motor through the foundation plate; and that the power pulley 84 turns the drive pulley 81 through a transfer belt 86 and a drive belt 87 and a pair of transfer pulleys 88 and 89 mounted on an intermediate stub shaft 91 extending downwardly from the foundation plate 56. The purpose of the transfer belts and pulleys is to obtain the desired speed ratio between the drive motor 83 and the drive pulley 81. The drive motor has two speeds, i.e., one relatively low speed in the clockwise direction and a second relatively high speed in a counterclockwise direction (both viewed from the top). When the motor rotates at its relatively low speed in the clockwise direction it also turns the drive pulley 81 at its lowest speed in a clockwise direction, as illustrated in FIG. 4. As shown in this figure, when the drive pulley 81 is turned by the drive belt 87, in a clockwise direction it tends to move downwardly on the helical threads 82 until it reaches the detent plate 92 secured to the bottom of the intermediate shaft 79. This plate presents a detent 93 which contacts a corresponding axial shoulder 94 depending from the drive pulley, when the drive pulley is in its lowermost position shown in FIG. 4. In this position, the drive pulley 81 is mechanically engaged with the intermediate shaft 79 through the detent 93, as well as through the helical gear teeth 82 and therefore drives the interme diate shaft clockwise. As indicated hereinbefore, in this position of the drive pulley 81 the cylindrical brake 72 prevents the outer shaft 69 and the gear box 68 attached thereto from rotating. However, the intermediate shaft 79 rotates freely inside the outer shaft so that an intermediate pinion 95, fixed to the upper end of the intermediate shaft 79, rotates therewith inside the gear box 68. This pinion 95 is in direct engagement with a first transfer gear 96 which, in turn, is mounted on and turns a stub shaft 97 rotatably mounted in the gear case. Rotation of the stub shaft 97 also turns a transfer pinion 98 keyed thereon, and the transfer pinion 98 drives an oscillating gear shaft 99 through a somewhat larger oscillating gear 10] fixed thereto. The oscillating gear shaft 99 also is mounted for rotation in the gear case and is connected to one end of an oscillating link 102 through a pin 103 mounted eccentrically on the 0s cillating gear 101. The other end of the link 102 is connected to the pivoted arm 104 of an arcuate oscillating gear rack 105 by a similar pin 106 attached to the arm. The arm 104 is pivotally mounted at one end on a shaft 

1. Washing and disinfecting apparatus comprising a washing and disinfecting tub, a storage tank for liquid disinfectant, a diverter valve connecting said tub either to a drainage system having means for removing washing and rinsing liquids or to said storage tank through a disinfectant piping system, said piping system having a reversible pump for transferring said disinfectant liquid back and forth between said storage tank and said tub, and first and second fluid level responsive means for rendering said pump inoperative as soon as the level of the disinfectant liquid drops below a predetermined point relative to said tank with respect to said first means and relative to said diverter valve with respect to said second means, and for again rendering said pump operative when even a small amount of said disinfectant brings the disinfectant level above the predetermined point with respect to said first means when the disinfectant is being transferred from said tub to said tank and above the predetermined point with respect to said second means when the fluid is being transferred from said tank to said tub. 